// Copyright (c) 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CC_OUTPUT_CONTEXT_CACHE_CONTROLLER_H_
#define CC_OUTPUT_CONTEXT_CACHE_CONTROLLER_H_

#include <cstdint>
#include <memory>

#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "base/memory/weak_ptr.h"
#include "base/single_thread_task_runner.h"
#include "cc/base/cc_export.h"

class GrContext;

namespace base {
class Lock;
}

namespace gpu {
class ContextSupport;
}

namespace cc {

// ContextCacheController manages clearing cached data on ContextProvider when
// appropriate. Currently, cache clearing is triggered when the Context
// provider transitions from Visible to Not Visible, or from Busy to Idle. As a
// ContextProvider may have multiple clients, ContextCacheController tracks
// visibility and idle status across all clients and only cleans up when
// appropriate.
class CC_EXPORT ContextCacheController {
public:
    class CC_EXPORT ScopedToken {
    public:
        ~ScopedToken();

    private:
        friend class ContextCacheController;
        ScopedToken();
        void Release();

        bool released_ = false;
    };
    using ScopedVisibility = ScopedToken;
    using ScopedBusy = ScopedToken;

    ContextCacheController(
        gpu::ContextSupport* context_support,
        scoped_refptr<base::SingleThreadTaskRunner> task_runner);
    virtual ~ContextCacheController();

    void SetGrContext(GrContext* gr_context);
    void SetLock(base::Lock* lock);

    // Clients of the owning ContextProvider should call this function when they
    // become visible. The returned ScopedVisibility pointer must be passed back
    // to ClientBecameNotVisible or it will DCHECK in its destructor.
    virtual std::unique_ptr<ScopedVisibility> ClientBecameVisible();

    // When a client becomes not visible (either due to a visibility change or
    // because it is being deleted), it must pass back any ScopedVisibility
    // pointers it owns via this function.
    virtual void ClientBecameNotVisible(
        std::unique_ptr<ScopedVisibility> scoped_visibility);

    // Clients of the owning ContextProvider may call this function when they
    // become busy. The returned ScopedBusy pointer must be passed back
    // to ClientBecameNotBusy or it will DCHECK in its destructor.
    std::unique_ptr<ScopedBusy> ClientBecameBusy();

    // When a client becomes not busy, it must pass back any ScopedBusy
    // pointers it owns via this function.
    void ClientBecameNotBusy(std::unique_ptr<ScopedBusy> scoped_busy);

private:
    void OnIdle(uint32_t idle_generation);
    void PostIdleCallback(uint32_t current_idle_generation) const;
    void InvalidatePendingIdleCallbacks();

    gpu::ContextSupport* context_support_;
    scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
    GrContext* gr_context_ = nullptr;

    // If set, |context_lock_| must be held before accessing any member within
    // the idle callback. Exceptions to this are |current_idle_generation_|,
    // which has its own lock, and weak_ptr_ and task_runner_, which may be
    // accessed from multiple threads without locking.
    base::Lock* context_lock_ = nullptr;

    uint32_t num_clients_visible_ = 0;
    uint32_t num_clients_busy_ = 0;
    bool callback_pending_ = false;

    // |current_idle_generation_lock_| must be held when accessing
    // |current_idle_generation_|. |current_idle_generation_lock_| must never be
    // held while acquiring |context_lock_|.
    base::Lock current_idle_generation_lock_;
    uint32_t current_idle_generation_ = 0;

    base::WeakPtr<ContextCacheController> weak_ptr_;
    base::WeakPtrFactory<ContextCacheController> weak_factory_;
};

} // namespace cc

#endif // CC_OUTPUT_CONTEXT_CACHE_CONTROLLER_H_
